This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. The kinase domain P4, transfers a phosphate group to the conserved histidine residue in the P1 domain of histidine kinase CheA. In this work we aim to determine the interaction between these two domains. Previous experiments have established that P1 domains are widely separated from each other and have considerable degree of freedom. In order to resolve the associated long distances, we use deuterated proteins from E.coli.